Method for leak testing and leak testing apparatus

Abstract

For leak testing closed containers ( 9 ) which are filled with a filling product containing at least one liquid component the container is introduced in a test cavity ( 1 ) which is evacuated at least down to vapor pressure of that liquid component. The pressure in the surrounding of the container ( 9 ) and thus within test cavity ( 1 ) is monitored. Monitoring is performed by a vacuum pressure sensor ( 7 ), whereas lowering pressure surrounding the container ( 9 ) is performed by a vacuum pump ( 5 ). Leakage is detected by monitoring a pressure change in the surrounding of the container which is due to evaporation of liquid emerging from a leak and being evaporated in the low pressure surrounding.

The invention claimed is: 
     
       1. A system for leak testing closed containers comprising:
 an apparatus for subjecting at least one container to test conditions and thereby monitoring a signal which is dependent on leak condition of said container; 
 means for simulating a leak to calibrate said apparatus; 
 wherein said apparatus includes at least one test cavity, a vacuum pump and a connection line communicating the test cavity with the vacuum pump, and wherein said means for simulating a leak includes a source of vaporized liquid communicated with said test cavity via said connecting line; 
 wherein said source of vaporized liquid includes a liquid reservoir and a needle valve in a line between said reservoir and said connecting line; 
 wherein said source of vaporized liquid further includes a pressurizing line connected to said reservoir and a valve in said pressurizing line for adjustably pressurizing liquid in said reservoir. 
 
     
     
       2. A system for leak testing closed containers comprising:
 at least one test cavity to receive at least one container to be tested; 
 an evacuation pump arrangement connected to the test cavity; 
 a leak simulating arrangement including a reservoir for a liquid and connected via an evaporation nozzle to the test cavity; 
 a pressurizing line for adjustably pressurizing the liquid in the reservoir, the evacuation pump arrangement and the pressurizing line providing an evaporation control arrangement. 
 
     
     
       3. The system according to  claim 2 , including a plurality of test cavities each for subjecting at least one container to test conditions, and wherein the leak simulating arrangement is connected in parallel to the test cavities. 
     
     
       4. The system of  claim 2 , wherein the evaporation nozzle is realized by a needle valve. 
     
     
       5. The system of  claim 2 , wherein the evacuation pump arrangement is connected to the test cavity via an evacuation line and the reservoir communicates with the test cavity by at least a part of the evacuation line. 
     
     
       6. The system of  claim 5 , wherein the evaporation nozzle is realized by a needle valve.